//
//  LYQTextField.m
//  LYQTools
//
//  Created by Alphts on 16/11/3.
//  Copyright © 2016年 Alphts. All rights reserved.
//

#import "LYQTextField.h"

@interface TextFieldDelegate : NSObject<UITextFieldDelegate>
@end

@implementation TextFieldDelegate

@end


@interface LYQTextField ()<UITextFieldDelegate>

@property(nonatomic,assign)NSInteger remainNum;

@property (nonatomic, strong) UITextField *tf;

@property (nonatomic, strong) TextFieldDelegate *fieldDelegate;

@end


@implementation LYQTextField

+(instancetype)textViewWithRemainNum:(NSInteger)remainNum{
    
    return [[self alloc] initWithRemainNum:remainNum];
}

- (instancetype)initWithRemainNum:(NSInteger)remainNum{
    if (self = [super initWithFrame:CGRectZero]) {
        self.remainNum = remainNum;

        self.fieldDelegate = [[TextFieldDelegate alloc] init];
        
        self.delegate = self.fieldDelegate;
        
        [self addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];
    }
    return self;
}

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField{
    
    return YES;
}


- (void)textFieldDidChange:(UITextField *)textField{
    
    UITextRange *selectedRange = [textField markedTextRange];
    //获取高亮部分
    UITextPosition *pos = [textField positionFromPosition:selectedRange.start offset:0];
    
    //如果在变化中是高亮部分在变，就不要计算字符了
    if (selectedRange && pos) {
        return;
    }
    
    NSString  *nsTextContent = textField.text;
    NSInteger existTextNum = nsTextContent.length;
    
    if (existTextNum > self.remainNum){
        
        //截取到最大位置的字符(由于超出截部分在should时被处理了所在这里这了提高效率不再判断)
        NSString *s = [nsTextContent substringToIndex:self.remainNum];
        
        [textField setText:s];
    }
}


- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    
    UITextRange *selectedRange = [textField markedTextRange];
    //获取高亮部分
    UITextPosition *pos = [textField positionFromPosition:selectedRange.start offset:0];
    //获取高亮部分内容
    //NSString * selectedtext = [textView textInRange:selectedRange];
    
    //如果有高亮且当前字数开始位置小于最大限制时允许输入
    if (selectedRange && pos) {
        NSInteger startOffset = [textField offsetFromPosition:textField.beginningOfDocument toPosition:selectedRange.start];
        NSInteger endOffset = [textField offsetFromPosition:textField.beginningOfDocument toPosition:selectedRange.end];
        NSRange offsetRange = NSMakeRange(startOffset, endOffset - startOffset);
        
        if (offsetRange.location < self.remainNum) {
            
            return YES;
            
        }else{
            
            return NO;
        }
    }
    
    NSString *comcatstr = [textField.text stringByReplacingCharactersInRange:range withString:string];
    
    NSInteger caninputlen = self.remainNum - comcatstr.length;
    
    if (caninputlen >= 0){
        
        return YES;
        
    }else{
        
        NSInteger len = string.length + caninputlen;
        //防止当text.length + caninputlen < 0时，使得rg.length为一个非法最大正数出错
        NSRange rg = {0,MAX(len,0)};
        
        if (rg.length > 0){
            
            NSString *s = @"";
            //判断是否只普通的字符或asc码(对于中文和表情返回NO)
            BOOL asc = [string canBeConvertedToEncoding:NSASCIIStringEncoding];
            if (asc) {
                
                s = [string substringWithRange:rg];//因为是ascii码直接取就可以了不会错
                
            }else{
                
                __block NSInteger idx = 0;
                __block NSString  *trimString = @"";//截取出的字串
                //使用字符串遍历，这个方法能准确知道每个emoji是占一个unicode还是两个
                [string enumerateSubstringsInRange:NSMakeRange(0, [string length])
                                           options:NSStringEnumerationByComposedCharacterSequences
                                        usingBlock: ^(NSString* substring, NSRange substringRange, NSRange enclosingRange, BOOL* stop) {
                                            
                                            if (idx >= rg.length) {
                                                *stop = YES; //取出所需要就break，提高效率
                                                return ;
                                            }
                                            
                                            trimString = [trimString stringByAppendingString:substring];
                                            
                                            idx++;
                                        }];
                
                s = trimString;
            }
            //rang是指从当前光标处进行替换处理(注意如果执行此句后面返回的是YES会触发didchange事件)
            [textField setText:[textField.text stringByReplacingCharactersInRange:range withString:s]];
        }
        return NO;
    }
}

@end















